Automatic transmission



Feb. 24, 1959 L. |MBLUM AUTOMATIC TRANSMISSION Filed April l1, 1955 15 sheets-sheet 2 I N V EN TOR. 50 /Mau/M BWM Fb. 24', 1959 L. IMBLUM AUTOMATIC TRANSMISSION 15 Sheets-Sheet 5 l Filed April 11. 1955 RIE-' INVEN'ToR. E0 /A//BMM Feb. 24, 1959 `l IMBLUM AUTOMATIC TRANSMISSION l5 Sheets-'Sheet 4 www,

Feb.f24, 1959 IMBLUM l 2,874,586

l AUTOMATIC TRANSMISSION Filed April 11, 1955 I 15 sheets-sheet 5 7 INVENroR. 50 /MBL UM Feb. 24,- 1959 Filed April 11, 1955 L. IMBLUM AUTOMATIC TRANSMIS'SON 15 Vsheets-sheetv '7 Feb.24, 1959 I L. MBLUM AUTOMATIC TRANSMISSION y 15 Sheets-Sheet 8 Filed April l1, 1955 www.

Feb. 24, 1959 Filed April 11, 1955 L. IMBLUM VAUTOR/Mmc TRANSMISSION 15 Sheets-Sheet l0 Feb. 24, 1959 v L. `|MBLUM 2,874,586

AUTOMATIC TRANSMISSION v Filed April i1, 1955 15 sheets-sheet 11 v /lr v Z' Tm y .923

nlrhhhh IN VEN TOR. V L50 /MBLUM 7 B I r 9.1,/ Qi; am I :E: :l: CEI- :5. Z ma?? Feb. 24, 1959 L. IMBLUM AUTOMATIC TRANSMISSION OOO 30A? 30A 2630K OOO v Wgr INVENTOR. E0 /MLz/M Feb, 24,1959

Filed April 11, 1955 1 IMBLUM AUTOMATIC TRANSMISSION :Eig-1 1 I5 L. VnvuaLLnm AUTOMATIC TRANSMISSION Feb. 424, 1959 15 Sheets-Sheet '14 Filedr April 11, 1955 2.56 F/FTH -z 6/ fana/em INVENTOR.

' 4101 ZELIG- 1 :z ww

L. IMBLUM 1 AUTOMATIC TRANSMISSIONl A Feb. 24, 1959 15 Sheets-Sheet l5 Filed April 1'1, 1955 INVEN TOR. L60 /Mw/W United States Patent Mice :2,814,586 AUTOMATIC TRANSMISSION Leo Imblum, Alameda, Calif. Application April 11,19ss,seria1,Na. 500,332

40 claims.' (ci. 74472 The `inventionrelates totransmission mechanisms which provide by means of a pluralityof gear sets and hydraulic `coupling means a variable speed drive from anweugine *or `other prime Vmover to a driven part, and which 1s responsive to engine speed to vshift automatically betwee'n `theseveralsets of gears.

An object of the present invention is to provide an automatic transmission of the character described lwhere- -in the plurality of gear-sets and uid lcouplingmeans'cooperate in improved mannento Yaiford smooth, quiet, positive and powerful shifting -between the gear sets; and wherein Vthe parts are-designed and constructed and op- -erate in a manner creatingfa Vbalanced system offsymmetrically applied vforces affording, in a minimum and a usable -size of unit, great strength, :high power and Vtorque transmission capacity coupled with extreme reliability *and durability of the mechanism. 'Y i nother object of the present Finvention -isito provide a transmission of the character labove 'described'in which the shifting operation may beeifected either automatically, as a function of engine speed, or manually, vand wherein Athe correlation between engine speed Vand 'automatic shifting is under continuous and instantaneous convtrol to provide an engine `shift range'faifording, as kfor example when applied "to automotive use, amultiplicity of drive options such as an immediate gain in torque transmission where required, o1' a decrease Ain jengine speed when permitted, and variable engine braking of vehicle .speed when desired.A Y.

Stillanfother` object of the present inventionis to proyide astrahsmirssion of the characterdescribed wherein the aforementioned "correlation between enginev speedand automatic shifting may be manually controlled by movernent of the accleratorrpedal for the `engine which controls the fuel dow tothe engine in a separate or conjoint `movernent; and may be automatically'controlled vwhere desired in accordance with grade, load and temperature conditions.

Yet a further object ofthe present invention is to provide an automatic transmission of the character above having a highoperating efficiency, andwhereinuid slippage and attendant loss of energy is confined entirely to the period of shifting between the several gear sets, and no uid energy 'loss occurs during operation ofthe transmission in any of the gear sets. i

Further objects fof the'present invention are to Vprovide an automatic transmission mechanism of the character described: `(1.) incorporating a uid' pump builtfitito the ,rotating system for elimination of seal problems ,and finstantaneous replacementof leakage; (2) incorporatinga reverse gear mechanism correlated in its function .with the forwarddrive mechanism; (3') -inrwhich provision lis `made'for coasting or towing and for starting of athe .en-

gine by motion vof fthe gear; V(4)r which will .automatically 2,874,586 Patented Feb. 24, 1959 accompanying and iforming. part of the 'specication It is understood, however, 'that variations in the showing made 1by 'the said drawings and description may be adopted withinthescope of the invention as set forth in `the claims.

"Referring 4to said drawings:

Figure `1 is a side-elevation of an automatic transmis sion"constructed -iniaccordance with the vpresent inven- At'itm/and shown inoperative association with parts of an automotive vehicle.

v.Figure 2 is an end elevation of the'transmission and associated parts `,illustrated in 'Figure 1.

Figure 3 is Valongitudinal vertical sectional view of the `transrriission.

Figuren 'is a cross-sectional `view taken substantially V'on the plane :of line l4--4 of Figure 3.

` Figure'Y 5 `is a fragmentary longitudinal sectional view fof'the" upper -portion of the transmission 4taken on an enlarged scale.

Figure 6 is a 'further Venlarged fragmentary cross-sec- *tional :view 'of a portion of the transmission taken Substantially on the plane of line 6-,6 of Figure 7.

f7isa fragmentary crosssectional view of the transmissionltaken'substantially.on the plane of line 7 7 35 pffFigure 6.

Figure -8 is an enlarged longitudinal Asectional view of a portion of the transmission adjacent A`the portion shown Figure 9 is an enlarged longitudinal sectional'view of a portion of the transmission adjacent the portion shown in Figure-8. n

p '-Figurell) `is `a cross sectional view of that part of `the "transmission illustrated in Figure 9 Vand Lis taken `substan- 't'iall-yjon the plane ,of line '10-10 of jFigure 9.

` Figure l`111 `is la longitudinal sectional view of a lower portion of ,the transmission.

"Figure 4112 is Va cross-sectional viewv of a part of the transmission shown in 'Figure 3 and is takensubstantially onit'he'plane of line 12-12 of Figure 13.

i -Figure lf3 is Aa cross-sectional view of the iiuid pump shown lin Figure l2 Vand is taken substantially on the plane'of llinej13--13 of Figure l2.'

Figure i4 is an enlarged fragmentary cross-sectional @View particularly showing the valve ports vlocated in the flower, ydriven shaft of the transmission.

Figure T5 is a schematic wiring diagram of certain of "the electrical parts used-in the transmission.

figure 16 is .a diagrammatic representation and graph fshowi'ng the homing and `timing means and coordinated coupling Iand decoupling `functions of the transmission.

Figure 17 is adiagrammatic representation and graph of the means and the graphical 'illustration vof vthe trans- Ymission operation obtained thereby under the various 'manually selectablefconditions. Y

Figure 18 is -a fragmentary cross-sectional view of the pumpfshown in Figure 3 and istakensub'stantially onthe plane-Ofiline 18--181of -Figure A3.

Figure v19 is Va fragmentary rear elevational view of a modified Vform of the `automatic transmission incorporatingmeans for controlling the shift pattern'of the trans,-

mission in accordance with the grade, load and temperature conditions.

Figure 20 is a fragmentary side elevation of the automatic transmission illustrated in Figure 19.

Figure 21 is a fragmentary plan view of the transmission illustrated in Figures 19 and 20.

Figure 22 is a fragmentary enlarged cross sectional view of one of the motor means used in the transmission illustrated in Figures 19-21.

Figure 23 is an enlarged fragmentary cross sectional View taken substantially on line 23-23 of Figure 19.

Figure 24 is a fragmentary cross sectional view taken substantially on the plane of line 24-24 of Figure 1.

The automatic transmission of the present invention consists briefly of input and output shafts 21 and 22, which carry a plurality of constantly enmeshed gear sets 23 and 24, 25 and 26, 27 and 28, 29 and 30, and 31 and 32, here providing ve forward speeds, and reverse gears 33 and 34, which are normally not engaged but which may t be enmeshed with a reverse idling gear 35; a plurality of fluid couplings more fully hereinafter developed connecting each of the gear sets to the shafts; a hydraulic shifter valve which is arranged and constructed to control the operations of the several fluid couplings so that upon movement of the shifter valve in one direction the couplings will be energized and de-energized to selectively engage the gear sets in the order of increasing gear ratio, and upon movement in the opposite direction through such positio-ns the gear sets will be engaged in the order of decreasing gear ratio; and means more fully hereinafter developed responding to the speed of the input shaft 21 to displace the shifter valve in its first mentioned direction as a function of decreased speed of the input shaft, and in an opposite direction as a function of increased speed of the input shaft.

Further important features of the present invention include manually operable means for taking over and superseding the automative operation of the transmission so that any of the several gears may be manually selected at will; means for manually controlling the correlation between the engine speed and automatic shifting and the coordinating of such means with the accelerator for the engine whereby the fuel ow to the engine and shift range of the transmission may be simultaneously controlled by conjoint movements of the accelerator pedal; the provision in the fluidcouplings of a hydraulic control for coasting or towing of a vehicle equipped with the transmission as well as for starting the engine of the vehicle by the motion thereof; provision of a homing device connected to the shifter valve and functioning when the latter is between positions to urge the shifter valve to the nearest of such positions and to deter hunting of the mechanism, and which functions in coordination with means limiting the speed of the shifting operation between the gear sets as a function of the input shaft speed, whereby shifting from one gear set to another will be smooth and positive at all operating speeds; the provision of a remote indicator for showing the position of the shifter valve and the vset of gears in operation; a control means for the reverse gear mechanism, which prevents automatic shifting into forward speeds while the reverse gear mechanism is in operation, and which additionally prevents shifting into reverse gear on automatic down shifting of the forward speeds; and various other features of advantage, which will be fully hereinafter set forth.

In accordance with the present invention, there is one gear in each of the sets of the constantly enmeshed gears which is journaled for free rotation on either the input or the output shafts, and the connection of this latter gear and shaft is under the control of a fluid coupling so that one fluid coupling is provided for each of the gear sets and controls the operation thereof. A typical showing of the uid couplings of the presentl invention will be best seen in Figures 6 and 7, and a description of this unit will suflice for all of the units. As will be seen from these figures, the couplings consist briey of concentrically arranged and relatively rotatable drive and driven membersff46 and 47, the former being mounted upon and keyed to the input shaft 21 for rotation therewith, and the latter including gear 25 which is enmeshed with gear 26 carried for rotation on the output shaft 22. Accordingly, it will be understood that so long as member 47 is freely rotatable on member 46, no drive connection between the input and output shafts will be effected by the enmeshed gears 25 and 26, but upon the restraining of members 46 and 47 for joint rotation, and to the extent that they are so restrained, the drive connection will be effected between shafts 21 and 22 through enmeshed gears 25 and 26. The member 46 is here of generally disk shape and is formed with concentric banks of circumferentially spaced axially extending open-ended cylinders 51 and 52, thc cylinders 51 in the outer bank here being twenty-four in number of which seventeen are shown in Figure 7 where seven identically constructed cylinders in the outer bank are deleted to obtain an adequate scale drawing. The cylinders 52 in the inner bank' are likewise twenty-four in number of which eighteen are shown in Figure 7 where six identically constructed cylinders in the inner bank are deleted in the interests of clarity of illustration.

VThe outer gear carrying member 47 is preferably of channel shaped annular form having a circumferentially extending `wall 106, which is journaled as by means of bearings 107 on the outer periphery 103 of the member 46 and is provided with inwardly projecting flange-like, axially spaced annular cam walls 109 and 110 having pairs of axially opposed cam faces 111 and 112, and 113 and 114 in juxtaposition to the opposite ends of the two banks of cylinders 51 and 52 respectively. In accordance with the present invention and as may best be seen in Figure 1l, the cam faces 111--114 are inclined to the axis, and the faces of each of the pairs are out of phase so as to approach and recede from the cylinder ends upon relative rotation of the members. Mounted for reciprocation in each of the cylinders 51 and 52 are pairs of opposed pistons 116 and 117 (in the case of cylinders 51) and 118 and 119 (in the case of cylinders 52), the pistons, in their extended positions, being engaged with and displaced by ring shaped bearing races 122, 123, 124 and 125 forming part of ball thrust bearings 131, 132, 133 and 134 running on the cam faces 111-114. t

A fluid pump 121 shown in Figures 3 and 18 is operatively connected to the cylinders and functions to supply uid under pressure therein between the pistons 116-119, to cause movement of the pistons against the cam faces 111-114 to apply coupling torque between the members 46 and 47; and as a feature of the present construction, the undulations of the pairspof cam faces 111-114 for the different banks are circumferentially staggered so that the coupling torque will be applied uniformly at circumferentially spaced positions around the axis of members 46 and 47.V The fluid used in the couplings is an incompressible liquid such as petroleum oil so that upon filling of the cylinders 51 and 52 with fluid, and upon locking of the fluid therein, the pistons will be locked in their outwardly extending position against the cam faces 111-114, and a solid geared connection is effected between the input and output shafts 21 and 22 through gears 25 and 26. Preferably the cams 109, 110 are constructed as separate, annular plates secured as by threading at their outer periphery to wall 106, thereby permitting some resilient flexing of their cam surfaces in an axial direction. Such'tlexing is limited by bearings 115 here located between the several axially spaced units. Preferably ball bearings are used generally throughout and at positions requiring high speeds. I prefer 4to interpose nylon or other non-metallic balls between the metal balls so as to eliminate sparking and erosion of the balls by reason of ,high speed metal ,to metal frictional contact. As another important: feature of :the ,huid coupling of the ,presentA invention `spring meansisfpro vided for normally holding .the 'pistons v11B-'411,9 1vin ."retracted position away from thecarn faces -so ,that in ,the absence of fluid pressure in .the cylinders Sli'iand 52, the members 46 and '47 will be fully and completely de`- coupled and may move `freely relatively to each" other on the bearings .107. .Such spring means .here .consists of a helical spring 126 mounted in tension between Leach of -the pairs of pistons 116 .and 117 in the outer `bank of cylinders 51, and a helical spring '127 similarlyfrnounted in tension between each .pair of pistons 118 Yaild2119 mounted in the inner `banl; of ycylinders 52, .thesprings operating in each case to normally urge theqpistons .to inwardly retracted position free from ,engagement wfith the cam faces 111-114. During coupling and ,decoupling operation frictional losses are reducedfby'the provision of annular bearings `131,132, 13.3`and 1.34vbe'- tween each of the cam faces 111-114 and .thelheadends of-pistons 116-119, the connection between theA Lpistons and the bearings here being effected to .permit ,necessary articulation `by parts 136, 13.7, 138 and 139 `having.,swivel connections in the head ends of pistons 116--119y and engaged with the bearing races as illustrated in Figures 6 and 11.

The operable connection of the pump 121 tothe cylinders l51 and 52 and the releasef of fluid 'from the cylinders are under the control of a shifter valve 141. In accordance with the present invention 4and as a principal feature thereof, `the drive shaft 21 is made of hollow tubular form, Vand the pump 121 and the shifter valve 141 are both mounted within the shaft sothat the entire fluid systems are centrally .contained within -the shaft 21 and the surrounding cylinder block members 46 of the fluid coupling, whereby the making .of uidconnections in the rotating system Vis ,greatly simplified, and seal problems substantially eliminated. Y

As will be seen from Figures 3 and 18, pump 121 consists of a pump housing 146 mounted internally of shaft 21 and for rotation therewith, and which contains enmeshed pump gears 147 and 148, the latter of which is driven by va shaft 149 ,projecting radially outwardly from shaft `2-1 for connection at its outer end with a drive gear 151 engageable with av stationary bevel gear 152 carried by abracket 153 extending from the top wall 154 of the transmission Yhousing 155. A iluidlevel is maintained in the housing 155 above the shaft 21 so fthat the pump housing 146 and its `intake passage 156 is constantly immersed in the fluid. Thefluid level is 6 25, 27, 29 and V31 consituting the `drive gears for the five forward speeds provided 'by jthe present .transmission and also carries Vgear 33 us'ed for reverse drive. A sabove noted, gears123,`25, 27, 29 and 31 Aarein constant `mesh with' gears '24, 26, 28, 30 and 32 carried by thedriven orlpropulsion shaft 22, and a fluid coupling `unitis fincorporated in one of the gears `makingup each set.` 'Since a Yprogressive decrease in gear diameter is desired valong thelength of shaft 21 while .contrariwise' a 'progressive increase in-diameter of `gears is provided along thfellength of the output shaft 22, Vit is convenient to' place vcertain ofthe fluid drive units in the gears on both shafts, that is to incorporate the'iluid ldrivein ythe "largest diameter Igears on these shafts. Thus, in accordance -w'ith the present construction a fluid coupling is incorporated Iin `the hubs of gears 23 and 25 on the drive shaft 21., and 'in the hubs of gears 28, 3,0, 32 and 34 mounted onshaft 22. Consistent with thisarrangement of the outputy shaft 2,2 is formed with a hollow tubular construction .in Vthe same manner 'as drive shaft 21, see Figures 3, '11 12 and 13, and carries an internally housed gearpump 1,81 and shifter val-ve 182. Gear pump 181 is driven byagear 183 carried by the drive shaft. As will be seen in Figure 3, gear 183 is enmeshed with gear 184 which isjournaled for rotation on -the shaft 22, and which carries with `it for rotation a bevel gear 187, which is inconstant `mesh with vthe drive gear 188 for pump '18,1fin thesame manner as the driving connection for pump 121." As will be understood from the foregoing, gear pump 1 21 carried by drive shaft 21 is in rotation as long as the engine of the vehicle is in Voperation and under such circumstances is driven by thestationary gear 1,52.' Also,luring operation of the engine and rotation 4vof shaft 21',`,gear 183 carried thereby constantly drives gears '184 v4and 187 on the output shaft 22 and accordingly Vdrives the pump gear 188 for supplying fluid under pressure Ato the shifter valve in the `propulsion shaft." The gear ratios effecting pump operation are selected so as to insure rotation of normally maintained to the height ofa plug 157 in the case and may be drained from a plug -15`8-pro'vided at the base of one of the end walls 159 of the housing. With further reference to the details of `construction `of transmission housing 155, it will be noted that the drive shaft `21 extends longitudinally between the `oppositeend walls 159 and 161 and is Vjournaled for rotation in ,a front'bearing 162 carried by a bearing cagew163 and at itsopposite rear end in a bearing 164 integrally housed by the .end wall 159. The forward end 166 of the drive -shaft pro jects externally of end wall 161 for vconnectionto the ilywheel 167 of the engine. A bell housing 168 secured to the forward end wall 161 serves to attach the transmission case to :the engine. FIhe-driven-or `propulsion shaft 22 is mounted in parallel relation toldrive shaft 21.and extends'longitudinally between the forward end wall 1 61 and the rear end wall 159. It is .journaledat its 4forward end in bearing 171 carried byftbearing cage 172, which is -in turn supported on the bottom wall 1730i the housing. vThe rear end 174 -of `the `.output shaft-is journaled ina bearing 176 integrally housed -in .the end wall 159 and projects rearwardly from `the wall 159 for connection to `the drive `shaftfof the automotive vehicle `or other .part -or piece ,of equipment yto be driven. Y

The imain drive shaft 21 carries the-driving `gears 23,

the pump gear 188 and a supply of uid pressureV in the output shaft 22 under all operating conditions (speeds of rotation) of the output shaft when fluid Vpressure is re'- quired therein for operating any of the fluid couplings carried thereby. The ends of the hollow shafts 21 and 22 projecting from the endwalls161 and 159 ofthe housing are appropriately sealed by .plugs 191 and 192.

Thedischarge port 196 of pump 121 is connected -to ,a pump ,pressureuid passage 197 `in the shaft21, Ysee Figure 5, from whence the iiuid 'ispicked up by the shifter valve 141 and carried longitudinally internallyV of the main or drive shaft 21 to service .the cylinders jof 'the rfluid couplings on the main shaft as well as for the automatic `controls later to be described. As understood, the discharge pressure of pump .121 will vary as a function of the speed of theA input shaft' 21V, and this function is utilized in several important ways in thepresent transmission. ',It is also desirable to be able to adjust thefluid-pressure particularly to compensate for wear of the pump, jand for ,this purpose a pressure control valve 198'is"h ere provided in the shaft 21 and in pump pressurepassage 197. Access tovalve 198 for adjustment may behadthrough 'aclosure plug 199 provided in the top vwall 15,4 of the housing in the plane of rotation of the valve 198. s f

In a similar manner the discharge port'201 ofthe huid pump 181 Vcarried in the output shaft'22jis` connected to a main pump pressure uid distributing passage 202 extending longitudinally through the `shaft 22' lfor supplying the uid couplings carriedby'the'propulsionshafn'see Figure ,11. The output vpressure of pump'181'alsovari'es with the speed of thepropulsionshaft'22, and preferably ,a pressure limiting Yvalve 203 vis carried by the propulsion shaft in the iuid passage 202.

Thearrangement of the cylinders 571 and 5,2 of veach of thefuid couplings together withtheiriiuidconnec'- tions Lisbes't seen in lFigllrefl 1of the drawings. v villlbe noted the cylinders Ainfthe outer Vbank 4are connectedV in f 7 Y groups of three cylinders 51a, 51b and Slt` for each group making eight groups in all spaced 45 degrees apart circumferentially around the cylinder block member 46. To accomplish this arrangement, a circumferentially extending passage 204 is provided for the cylinders 51a, 51b and 51c comprising each group to connect the cylinders of the group. In asimilar manner, the cylinders in the inside bank are connected together in groups of three 52a, 52b and 52e, thus providing eight groups of cylinders spaced circumferentially apart by 45 degrees in the same manner as the groups of cylinders in the outer bank. As will be noted, passages 216 and 217 connect the cylinders 52a, 52b and 52C together as a group, and like passages are provided to connect the other seven groups of inside cylinders.

Each of the groups of cylinders is connected by an individual fluid circuit. `Eight radially extending passages 221 connect the eight groups of cylinders in the outside bank to eight circumferentially spaced longitudinally extending passages 231 in the main shaft 21. In a similar manner the eight groups of cylinders in the inside bank are connected by eight radial passages 241 to eight circumferentially spaced longitudinally extending passages 251 in the drive shaft 21. As will be seen from Figure 7, the radial passages 241 for the inner bank of cylinders are spaced circumferentially between the radial passages 221 for the outer bank of cylinders.l Preferably all of the longitudinally extending passages 231 and 251 are arranged in circumferentially spaced relation equally distant from the center of the shaft and positioned with the longitudinal passages 231 servicing the outside bank of cylinders spaced circumferentially between the longitudinal passages 251 servicing the inside bank of cylinders.

In accordance with'the present invention, each pair of opposed cam faces 111-112 and 113-114 provide one undulation or cycle for each revolution; for example with reference to Figures 6 and l1 it will be seen that the opposed cam faces 111-112 are at their widest point at the top of the views so that the opposed pistons 116 and 117 will be forced together upon relative displacement oi the members 46 and 47 through 180 degrees of rotation from the position illustrated in the figures, and such pistons will complete one cycle of reciprocation reaching vtheir outmost and innermost positions during one complete revolution of relative movement between members 46 and 47. In a similar manner, opposed cam faces 113-114 are illustrated at their narrowest position at the ytop of the views and at their widest apart position at the bottom of the views, thus placing these cam faces substantially 180 degrees out of phase with cam faces 1111-112. In this fashion, diametrically equal forces are created around the axis of the uid coupling unit so `that the stresses are distributed. This circumferential distribution of forces around the axis of the unit coupled with the axially opposed forces of the pistons themselves enable the construction of a compact, strong and balanced unit of relatively very high torque and power transmitting capabilities.

y Cooperating with the diametrical out of phase relation of the two pairs of cam faces, the iluid circuit is arranged to connect the diametrically opposed groups of cylinders in the inner and outer banks for joint operation. Thus cylinders 51a,` Slb and 51C of the outside bank are connected to diametrically opposed cylinders 52a, 52b and 52C of the inside bank and the'pistons in these two groups ofcylinders will simultaneously apply their torque generating gripping actions. It is desirable that only the diametrically opposed groups of inner and outer cylinders be "connected together so as to avoid a pumping action of uid between the cylinders. To accomplish this connection of diametrical groups, while isolating them from `Aeach Vofhthe'other connectedgroups, there is provided at ,the` inner side'- of the longitudinal passages231 and 251 a series of eight axially spaced' annular fluid collecting 8 rings 261-268, one in number for each of the cylinder groups. Each of the eight longitudinal passages 251 (for the inner cylinders) is connected to one of the collector rings 261-268 by a radial passage 271 and each of the eight longitudinal passages 231 (for the outer cylinders) is connected to the same collector rings 261-268 by radial passages 272 thereby placing the diametrically opposed pairs of groups of cylinders in the inner and outer banks in common uid connection. For example with reference to Figure 7, it will be seen that cylinders 51a, 51b and 51C in the outer bank of cylinders at the bottom of the view are jointly connected by circumferential passage 204, by radial passage 221, longitudinal extending passage 231, radial passage 272 to collector ring 261. At the opposite (upper) side of the cylinder block, the opposed group 52a, 52b and 52C of inner cylinders are jointly connected by passages 216 and 217, radial passage 241, longitudinal passage 251, radial passage 271 to collector ring 261 thereby placing the upper group of cylinders 52a, 52b and 52e in common tluid connection with the lower group of outside cylinders 51a, Slb and 51e. In an identical manner each remaining group of diametrically opposed cylinders is connected to one of the collector rings 262- 268.

In the case of the main drive shaft 21 here two fluid coupling units are provided in the hubs of gears 23 and 25; it is desirable that the uid passages for the hydraulic cylinders for both of the couplings be brought longitudinally through the shaft to a common valving station so that the charging and discharging of these cylinders to control the operation of the uid coupling units may be conveniently effected by relatively short strokes of a common selector or shifter valve 141. To do this and to provide for individual intake and discharge passages for each of the eight connected groups of cylinders, the eight collector rings 261-268 are connected to sixteen inwardly positioned and circumferentially spaced longitudinally extending passages (a pair 231 and 282 for each collector ring, see Figures 6 and 7), which are in turn connected to the interior peripheral wall 297 of the drive shaft 21 in a series of eight inlet ports 301 and eight discharge ports 311 which open to the wall in a common transverse plane. The fluid collector rings for the other fluid coupling on the shaft are similarly brought to a series of sixteen circumferentially spaced inlet and discharge ports located in a common transverse plane axially adjacent to the transverse plane of the ports 301 and 311, as shown at :Silla and 311a.

The shifter valve 141 is here of cylindrical form having an external periphery 319^slidablymounted for reciprocation on the internal wall 297 of a sleeve 320 carried internally by the shaft, and the valve is provided in a common transverse plane with sixteen circumferentially spaced ports comprising eight pump pressure ports 321 which are spaced for registration with the inlet ports 301, and eight reservoir connected ports 331 positioned for registration with the shaft discharge ports 311 for receiving uid from the cylinders for return to the reservoir (here represented by the transmission housing) under special circumstances later described. Normally, the evacuation of the cylinders is effected by a pair of axially spaced, annular reservoir connected valve ports 341 and 342 which are interconnected by passages 343 (see Figure 7) and are arranged for registration with the discharge ports 311' in axially displaced positions of the shifter valve. As here shown, the shifter valve is provided with a central hollow core 349, which opens by way of a port 351, see Figure 5, to the hollow interior of the shaft 21 from whence fluid may pass into the housing and to the suction side of pump 121. The reservoir passage 349 is connected to the valve ports 341 and 342 by a radial passage 352, see Figure 6. The secondary valve reser- Voir ports 331 are connectedto the main reservoir passage 349 by way of a longitudinally extending valve chamber 353 provided in the shifter valve and connected adiaent one end to port 331 and-mediauy grits length by radial passage 354 to the `center core passage 349.' In normal operation, ports 331 areV closed by a spring loadedv checkvalve356 in the chamber 353 and passage 354is closed by a spring loaded slide valve 357 also in the chamber 353. Connection of the pump pressureY valve ports 321 iseifected by a series of' radial passages 358 which extend from the ports inwardly to a longitudinally extending annular' pump pressure fluid passage 359, which extends longitudinally of the shifter valve and is connected by port 361 at the end of the shifter valve to the pump pressure passage 197 in the drive shaft, see Figure 5. Fluid under pressure is thus supplied bypump 121 to the pump pressure passage 359 in the shifter valve `and through the eight radial passages 358 to the pumppressure ports 321 and thence outwardly through lthe aligned ports 301 in the shaft and the registering passages V281 leading to the cylinders.

`As an important feature of the present construction a unidirectional valve means is 'provided in the last mentioned intake passages so that fluid will flow only in an outward direction in these passages Vto the cylinders and return flow from the cylinders will be checked. For this purpose a ball check valve 362 is provided in the eight intake passages 281 for lthe cylinders. In this manner uid supplied under pressure to the `cylinders-will urge apart the pistons therein into coupling relation with the cam faces, and releaseof the fluid, to permit retraction of the pistons, is solely and exclusively under the control of disch-arge passages 282 and their ports 311.

With reference to Figure 6, the shifter Valve isin position placing its pump pressure ports 321 in registration with the shaft inlet ports 301 whereby uid under pressure lis passed to the cylinders of the fluid coupling contained in gear 25. At the same time, a land 363 on the slide valve between reservoir ports 341 -342 covers the cylinder discharge ports 311 with the exception that the valve ports 331 formed in the land are in registration but are closed by valves 356 and 357. In this condition the pistons in the cylinders are forced outwardly into full coupling engagement with the cam faces 111-114, and joint rotation of the gear 25 and the drive shaft is effected. At the same time, valve reservoir port 341 is connected to the discharge ports 311a'of the adjacent vfluid coupling for gear 23. Pistons `in this fluid lcoupling Aare accordingly retracted by their springs 126 and 127 away from the cam faces whereby gear I23 is journaled for free rotation on the drive shaft. As 'the Ashifter valve is moved to the left, `from the position illustrated in Figure 6, valve land 363 starts to close olf the discharge ports 311a; and upon further movement pump pressure valve ports 321 start into registrationwith the inlet shaft ports 301a for the fluid coupling for gear 23. Fluid pressure thus opens'thecheckvalve 362:1 for the second fluid coupling and starts the fluid flow into the cylinders for urging apart the pistons therein. 'While the second coupling is taking hold, these pistons reciprocate in their cylinders as relative rotation between the coupling members takes place, the discharge of the cylinder fluid being permitted by the restricted but still open discharge `ports 311a. As the shifter valve is moved further to the left, the discharge ports 31111 are gradually closed o'f so as to lock the pistons against reciprocation and thereby fully couple the members. In all of the latter positions, the supply of fluid under pressure is maintained to the cylinders so as to `constantly replenish any leakage which takes place and return movement `of theuid'through the pump pressure passage is stopped by check valve 362:1.

During the course of progressive energizing of thesesond fluid coupling, as above described, the rst iluid coupling is progressively de-energized so that a `smooth transition takes place from one to the other. As will be observed from Figure Y5, the fshifter valve on moving to the left progressively moves land 363 away from ports `311 while progressively vbringing reservoir Sport 3'42 into its operation. `means is provided for Vrendering pump '181 effective to `,energize theuid couplings when for Vexampleif is `desred to start 'a dead engine by pushing of the vehicle `In .such case, gear i187, entrained `totheengine shaft, 4is stationary, tand rotation of the propulsionshaft `22 causes v S10 registration therewith; and at the same time irst maine tainingv connection of the pump pressure ports 321 and the shaft inlet ports 301 and thereafterclosing off ports 321 so as to thereby slowly and progressively release increasing quantities of fluid from the cylinders of tlie iirst fluid coupling and effect gradualdecoupligrthereof.

As will be understood the transmission of torque between the coupled members accomplished by the closing off of the discharge ports 311 generates hydraulicfpressure within the circuits of the fluid coupling, which is retained by check valves 362 and ,pressure control valves 356 and 3,57 thereby locking the pistons against thecam faces. Since the cam faces are tlat over 360 degrees, four of the circuits will operate in compression while their pistons are being driven inwardly by the converging cam faces. The other four circuits operate on their fluid charging strokes wherein iluid is applied through the check valves 362. Pistons operating inwardly along the slopes of the cams remain under compression until the end of the converging slopes at which point the pistons are forced outwardly against the diverging cam slopes and under such circumstances change from pressure producing to pressure receiving status, which continues until the pistons reach the ends of the `divergent cam slopes, at which point they again enter the .compression convergent phase of the operation. After full closing of the cylindery discharge passages, the pistons will remain static for normal load conditions, except for leakage and the imposition of sudden high lloads later .described. The occurrence of leakage will only cause Vslow creeping action of the pistons as successive groups of pistons are slowly advanced over the convergent carri slopes providing at all times continuous torque transmission.

Since the check valves 362 are mounted in the shaft for radial movement, they are subject to opening Vaction by centrifugal force. `Accordingly, it is desirable to provide some means for counterbalancing these check valves so as to yhold them closed at al-l shaft speeds. As here shown, leaf type springs 367 are used for urging valves 362 to their seats and Weights 368 are mounted on cantilever arm portions of the springs for counterbalancing the valves 362.

As an important feature of the present transmission, the valves 356 and .357 provide means for controlling .the release `of fluid from the cylinders and thereby function to limit the torque applied. A sudden load thrown on to the fluid coupling, such as by rapid down shifting, compression braking `of the vehicle, or the like willl increase the fluid pressure in the circuits suicient to force open valve 356, against the rresistance of its closing spring 369, which renders the valve pressure responsive.

An instantaneous high load will simply pop open valves 356 and vsquirt `minute quantities of uid into valve chamber 353, thervalves 356 functioning to snap closed as soon as the instantaneous load passes. If the over load is sustained, valves v356 will remain open, lmore fluid will `be discharged :into valve chamber 353 and slide valve 35.7

will be moved against the resistance of .its closure vspring 371,-until the valve uncovers passage 354 therebyventing valve chamber 353 to the reservoir passage 349. Upon passing of the over load, spring 369 will restore valve 357 in closing relation against vpassage, 354, as illustrated in Figure 6, 'the valve 357 having apredetermined -clear- `ance'to permit such return and being normally retained in returned position against a stop 372. 4

As-above described, gear pump 181 is normally operated by the engine drive shaft 21 and, as will beunderstood, the gear type pump is inherently unidirectional in In accordance with the present invention rotation of pump-gear 188 in a normally reverse diret;- 

